Linked color imaging (LCI), a novel image-enhanced endoscopy technology, emphasizes the color of early gastric cancer

Abstract

Background and study aims: Linked color imaging (LCI) and blue laser imaging (BLI) are novel image-enhanced endoscopy technologies with strong, unique color enhancement. We investigated the efficacy of LCI and BLI-bright compared to conventional white light imaging (WLI) by measuring the color difference between early gastric cancer lesions and the surrounding mucosa.

Patients and methods: Images of early gastric cancer scheduled for endoscopic submucosal dissection were captured by LCI, BLI-bright, and WLI under the same conditions. Color values of the lesion and surrounding mucosa were defined as the average of the color value in each region of interest. Color differences between the lesion and surrounding mucosa (ΔE) were examined in each mode. The color value was assessed using the CIE L*a*b* color space (CIE: Commission Internationale d'Eclairage).

Results: We collected images of 43 lesions from 42 patients. Average ΔE values with LCI, BLI-bright, and WLI were 11.02, 5.04, and 5.99, respectively. The ΔE was significantly higher with LCI than with WLI ( P < 0.001). Limited to cases of small ΔE with WLI, the ΔE was approximately 3 times higher with LCI than with WLI (7.18 vs. 2.25). The ΔE with LCI was larger when the surrounding mucosa had severe intestinal metaplasia ( P = 0.04). The average color value of a lesion and the surrounding mucosa differed. This value did not have a sufficient cut-off point between the lesion and surrounding mucosa to distinguish them, even with LCI.

Conclusion: LCI had a larger ΔE than WLI. It may allow easy recognition and early detection of gastric cancer, even for inexperienced endoscopists.

Fig. 1

Imaging characteristics of the linked color imaging (LCI) and blue laser imaging (BLI)-bright modes.

Fig. 2

Image processing method used in the current study. a The image of the lesion is prepared, and the area of interest is extracted. b The border line between the lesion and surrounding mucosa was drawn based on the histological examination of the resected tissue using endoscopic submucosal dissection and other endoscopic images captured through the procedure including with magnification. c The inside and outside lines are drawn equidistant from the border line. d A rectangle intersecting the lesion along the minor axis of the stomach is drawn. The regions of interest (ROI) of the lesion and the surrounding mucosa are enclosed within these lines. The color value of the lesion and surrounding mucosa is represented by the average value within each ROI. The color difference between the lesion and surrounding mucosa (ΔE) is the difference between the averaged color value in the ROI of the lesion and the ROI of the surrounding mucosa.

Fig. 3

The image of process of color analysis by each mode. WLI, white light imaging; BLI, blue laser imaging; LCI, linked color imaging.

Fig. 4

The CIE L*a*b* color space (CIE: Commission Internationale d’Eclairage). The CIE L*a*b* color space is a color-opponent space with three dimensions: L* (i. e., lightness), a* (i. e., red to green), and b* (i. e., yellow to blue). The color difference between the lesion and surrounding mucosa (i. e., ΔE) is calculated in the L*a*b* space as the distance between 2 points (black double arrow). It approximates the visual differences detected by the human eye.

Fig. 5

A flowchart demonstrating the selection of patients and lesions. ESD, endoscopic submucosal dissection.

Fig. 6

Color value of the lesion and surrounding mucosa. Columns L*, a* and b* indicate the color value of each dimension. The subscript “l” and “s” indicate “lesion” and “surrounding mucosa,” respectively. WLI, white light imaging; BLI, blue laser imaging; LCI, linked color imaging.